WASHINGTON — President Trump is poised in the coming days to announce his plans to dismantle the centerpiece of President Barack Obama’s climate change legacy, while also gutting several smaller but significant policies aimed at curbing global warming.

The moves are intended to send an unmistakable signal to the nation and the world that Mr. Trump intends to follow through on his campaign vows to rip apart every element of what the president has called Mr. Obama’s “stupid” policies to address climate change. The timing and exact form of the announcement remain unsettled, however.

The executive actions will follow the White House’s release last week of a proposed budget that would eliminate climate change research and prevention programs across the federal government and slash the Environmental Protection Agency’s budget by 31 percent, more than any other agency. Mr. Trump also announced last week that he had ordered Scott Pruitt, the E.P.A. administrator, to revise the agency’s stringent standards on planet-warming tailpipe pollution from vehicles, another of Mr. Obama’s key climate change policies.

While the White House is not expected to explicitly say the United States is withdrawing from the 2015 Paris Agreement on climate change, and people familiar with the White House deliberations say Mr. Trump has not decided whether to do so, the policy reversals would make it virtually impossible to meet the emissions reduction goals set by the Obama administration under the international agreement.